1. Field of the Invention
Aspects of the present invention relate to an information recording medium, a recording and/or reproducing apparatus, and a recording and/or reproducing method enabling information recorded on a medium implementing logical overwrite to be more efficiently reproduced.
2. Description of the Related Art
High density optical discs, such as Blu-ray discs (BDs) and high-definition digital versatile discs (HD DVDs), have been developed and have begun to be distributed in the marketplace. For such optical discs, methods for increasing capacities of the optical discs have been attempted, such as reduction of track intervals and pits by using a single-wave light source, and stacking a plurality of recording and/or reproducing layers in one disc. Such attempts can be seen from the evolution of compact discs (CDs), digital versatile discs (DVDs), the HD DVDs, and the BDs. Apart from methods for increasing capacities of the optical discs, in the case of a BD-recordable (BD-R) disc, a logical overwrite method has been suggested as a method of rewriting data of the BD-R disc at an identical logical address in order to more conveniently use the BD-R write-once disc. The drawback of this method is that, as more logical overwrite operations are performed, fragmentation of data increases, and the amount of data indicating overwritten areas and areas for replacing the overwritten areas also increases. Accordingly, data access time increases.
FIG. 1A is a diagram illustrating a logical structure of a typical single-layer optical disc. Referring to FIG. 1A, the single-layer optical disc includes an arrangement of an inner zone 110, a data zone 120, and an outer zone 130. The inner zone 110 includes a lead-in area 111; the data zone 120 includes an inner spare area 121, a user data area 122, and an outer spare area 123; and the outer zone 130 includes a lead-out area 131. Allocation of the inner spare area 121 and the outer spare area 123 is determined according to whether defect management is employed for the single-layer optical disc. If defect management is employed, replacement data for replacing defect data is recorded in these areas.
FIG. 1B is a diagram illustrating a logical structure of a typical double-layer optical disc. Referring to FIG. 1B, the double-layer optical disc includes a recording layer 0 and a recording layer 1. The recording layer 0 includes an arrangement of an inner zone 0 (140), a data zone 0 (150), and an outer zone 0 (160). The inner zone 0 (140) includes a lead-in area 141, and the data zone 0 150 includes an inner spare area 0 (151), a user data area 0 (152), and an outer spare area 0 (153). The recording layer 1 includes an arrangement of an inner zone 1 (170), a data zone 1 (180), and an outer zone 1 (190). The inner zone 1 (170) includes a lead-out area 171, and the data zone 1 (180) includes an inner spare area 1 (181), a user data area 1 (182), and an outer spare area 1 (183).
Logical overwrite in a write-once disc will now be explained. Due to a characteristic of the medium (e.g., the write-once disc), it is impossible to physically overwrite a written area in the write-once disc. However, techniques can be implemented so that data is as if overwritten on a part of the write-once disc in which data has already been recorded. This is referred to as logical overwrite.
FIG. 2 is a diagram illustrating a write-once disc in which three tracks are allocated according to a typical technology. A disc can be used after being divided into a plurality of tracks, and FIG. 2, shows that a user data area 122 is divided into three tracks numbered 1, 2, 3, and data is recorded in part of a track 1 and part of a track 2. In FIG. 2, NWA indicates a next writable address. In track 1, the next writable address is marked as NWA 1.
FIG. 3A is a diagram illustrating a typical technique where a logical overwrite is performed in a track by allocating a replacement area in an unrecorded area of the track. Referring to FIG. 3A, if a request to write data at an area with an address less than or below an address NWA 1 of the track 1 (i.e., in an area (A) in which data is already recorded) is received, the area (A) is registered as a defect area in a defect list, or the area (A) is registered as a defect area in a separate overwrite list. Then, data of the area (A) is recorded in an area (B) which begins from the NWA 1.
FIG. 3B is a diagram illustrating a typical technique where a logical overwrite is performed in a track by allocating a replacement area in an inner spare area 121 that is separate from the track. Referring to FIG. 3B, if a request to write data at an area with an address less than or below an address NWA 1 of the track 1 (i.e., in an area (A) in which data is already recorded) is received, the area (A) is registered as a defect area in a defect list, or the area (A) is registered as a defect area in a separate overwrite list. Then, data of the area (A) is recorded in a predetermined area (B) of the inner spare area 121.
In the disc in which a logical overwrite operation is performed in these ways, a reproducing apparatus refers to the defect list or the overwrite list, and reproduces data that should be reproduced from an area that is registered in the list as a defect area from a replacement area instead. The defect list or the overwrite list is stored in a lead-in area or a separate system area.
FIG. 4A is a diagram illustrating a typical example of a defect list and FIG. 4B is a diagram illustrating a typical example of an overwrite list. The first entry of the defect list indicates that replacement data to replace data recorded in a defect address 100h is recorded at a replacement address 200000h. The second entry of the defect list indicates that replacement data to replace data recorded in a defect address 230h is recorded at a replacement address 200001h, and the third entry of the defect list indicates that replacement data to replace data recorded in a defect address 440h is recorded at a replacement address 200002h. Each entry illustrated in FIG. 4B is identical to that illustrated in FIG. 4A, and only the names of the lists are different from each other.
As logical overwrite in a write-once disc is implemented in ways discussed above, if more logical overwrite operations are performed as data is recorded, data fragmentation, in which logically continuous data is physically fragmented and then recorded, increases.
FIG. 5A is a diagram illustrating data fragmentation that typically occurs when logical overwrite is performed in a track of a disc by allocating a replacement area in an unrecorded area of the track. Referring to FIG. 5A, a file A and a file B are recorded in a track (i.e., track 1). It is also shown that data in an area 510 of the file A is replaced by replacement data in an area 540, data in an area 520 of the file A is replaced by replacement data in an area 550, and data in an area 530 of the file B is replaced by replacement data in an area 560.
In this state, if a reproducing apparatus is to read the file A, a reproduction order thereof is performed as follows. That is, the reproducing apparatus reads a part of the file A indicated by reference number 1 and then, jumps to the area 540 that replaces the area 510 and reads data indicated by reference number 2. Then, the reproducing apparatus returns to and reads a part of the file A indicated by reference number 3, and then, jumps to the area 550 that replaces the area 520 and reads data indicated by reference number 4, and then, returns again to and reads a part of the file A indicated by reference number 5 to complete a reading of the file A.
FIG. 5B is a diagram illustrating data fragmentation that typically occurs when logical overwrite is performed in a track of a disc by allocating a replacement area in a spare area that is separate from the track. Referring to FIG. 5B, a file A and a file B are recorded in a track (i.e., track 1). It is also shown that data in an area 510 of the file A is replaced by replacement data in an area 540 in an inner spare area 121, data in an area 520 of the file A is replaced by replacement data in an area 550 in an outer spare area 123, and data in an area 530 of the file B is replaced by replacement data in an area 560 of the outer spare area 123.
In this state, if a reproducing apparatus is to read the file A, a reproduction order thereof is performed as follows. That is, the reproducing apparatus reads a part of the file A indicated by reference number 1 and then, jumps to the area 540 that replaces the area 510 and reads data indicated by reference number 2. Then, the reproducing apparatus returns to and reads a part of the file A indicated by reference number 3, and then, jumps to the area 550 that replaces the area 520 and reads data indicated by reference number 4, and then, returns again to and reads a part of file A indicated by reference number 5 to complete a reading of the file A.
If data fragmentation increases due to an increase in logical overwrite operations as described above, seek operations for replacement data occur frequently when a file is reproduced, thereby increasing the access or seek time. Also, data fragmentation increases the size of the defect list or the overwrite list, thereby making management of the list more difficult. That is, a search time of the defect list or the overwrite list increases, more time for registering new entries is needed, and more management areas for recording the defect or the overwrite lists in the lead-in area are needed.